Ecomorphological groups in oribatid mite communities shift with time after topsoil removal – Insight from multi-trait approaches during succession in restored heathlands

Restoration of nutrient-enriched heathlands and similar dry habitats via topsoil removal requires the re-assembly of above and belowground communities to attain fully functional ecosystems. Top-soil removal provides unique opportunities to study the assembly processes, but research has traditionally focused on succession of the aboveground part of the ecosystem. Oribatid mites are a dominant group of soil mesofauna in the belowground part of heathlands. They possess attributes for bioindication and have shown high sensitivity to environmental changes during succession. However, few studies have focused on changes in functional community profiles and the factors shaping them with time. We sampled heathlands of different restoration ages located in East Belgium, studied traits of oribatid mite communities of a chronosequence, and assessed the interaction between traits and abiotic variables using community weighted means (CWM) and an iterative co-correlation analysis between abiotic parameters, species trait attributes and species abundances (iterative RLQ analysis). Our study suggests that moisture preferences, concealability (i.e. defence mechanism against desiccation and predation), and body length were the dominant traits structuring the oribatid mite communities. We found that both dispersal and environmental filters shape the assembly of oribatid mite communities, but these drivers dominate different stages of succession. Moreover, trait assemblages deriving from three well-defined eco-morphological groups closely followed these constraints in time. Thus, the shifting dominance of specific groups provides valuable insight on the soil community functioning in a changing environment.